Lead poisoning in heifer mob

Time and location: September 2019, Katherine NT.

Case definition: Four heifers in a mob of 21 died shortly after showing acute neurological signs (blindness, frenzy, staggering, seizures) following exposure to lead batteries in the property rubbish dump.

Gross findings: One animal was euthanised. Abrasions and contusions to skin, limbs and head were attributed to its behaviour and being tangled in the fence prior to death. The brain appeared very congested. There were no other gross findings. Samples submitted included EDTA blood, and fresh and fixed tissues: brain, spinal cord, skeletal muscle, liver, lung, heart, spleen, lymph node and GIT.

Laboratory findings: The field diagnosis of lead poisoning was confirmed by blood lead analysis. EDTA blood Lead analysis = 1.15ppm (mg/L). Results above 0.5ppm are conclusive for lead intoxication. Histopath and exclusion testing for Lyssavirus, rabies, Aujeskzy’s disease are still in progress.

Animal / management / environment risk factors: A small mob of 21 heifers were in the laneway which had access to the property rubbish dump because the fence had fallen down. The animals that died had all been in the dump, where batteries had been chewed, but it was not clear whether the others had been in the area.

Context: Lead poisoning is a reportable disease because lead exposure may have serious consequences for human health, particularly for young children. Even low levels of exposure can irreversibly affect brain development. Food-producing animals exposed to lead are subject to movement and slaughter restrictions to ensure food safety and product integrity as their products may pose a risk if consumed by people or other animals. Northern Territory restrictions depend on the extent of toxicity. Affected animals may carry a lead status for life and be unsaleable, or may be eligible for re-testing and slaughter with removal of offal from the food chain.  Lead status is put on the NLIS tag of individual animals which cannot be exported or slaughtered for consumption, other than in some (rare) cases, where the meat can be added to other fresh meat and fed to crocodiles in the commercial skin trade, where the meat is not harvested for consumption.

Recommendations to the producer: The 17 other cohorts in the mob were tested for lead to ensure they did not exceed the Maximum Level (ML) allowable under the Australian & NZ Food Standards Code. They were all below the ML so no further action is required. The station rubbish dump was fenced to prevent livestock access.